Method of drilling wells in rock



Dec. 23, 1969 v, G. STEWART METHOD OF DRILLING WELLS IN ROCK 2 Sheets-Sheet 1 Original Filed Oct. 6, 1967 Vernon fORA/EY Dec- 23, 1969 v. G. STEWART METHOD OF DRILLING WELLS IN ROCK Original Filed Oct. 6, 1967 2 Sheets-Sheet 2 R. Ww @m ,rv JW 6. m y V /2 ATTORNEY United States Patent O lU.S. Cl. 166-315 4 Claims ABSTRACT F THE DISCLOSURE In order to eihciently utilize a percussive drill and air compressor of the size conventionally found in the field in making both the upper part of the hole to be cased and the remainder of the hole of substantially reduced diameter, a rst hole is drilled from the surface, is then enlarged and casing cemented therein. Then the smaller remainder of the hole is drilled through the set casing, the

velocity of the chip carrying exhaust from the drill motor being maintained to the surface due to the restricting effect of the surface casing.

This application is a division of my copending application Ser. No. 673,318 led Oct. 6, 1967 now abandoned. This invention relates to methods for drilling wells and consists particularly in novel method for efficiently using percussive equipment for this purpose.

In the drilling of water wells, health regulations frequently require the secure casing of the upper portion of the wells to exclude ground Waters and contaminants therefrom. This necessitates the drilling of the upper part of the hole at a substantially greater diameter than the remainder of the hole. For instance, where the major portion of the hole is on the order of 6-6% inches in diameter, a normal dimension, the upper portion of the hole must be 8 or l0 inches in diameter in order to receive the sealing casing and securing cement therearound. However, the drilling equipment customarily available, including the most widely available compressors of 450 cu. ft. per min. (standard) capacity, while being adequate and eicient for drilling a 6-63A-inch hole with the use of a 51A-inch percussion motor at 100 or 200 p.s.i., is not adequate or eicient for drilling an 8- or lO-inch hole during the rst 40 feet or so for the application of the ground casing. The problem is accentuated where even the upper portion of the hole must be drilled through hard rock. The result is that drillers, in attempting to use their available drilling equipment, require much longer time for drilling the large part of the hole in which the casing is to be set, and the bit life is greatly reduced.

Where conventional rotary equipment is used with cone-type bits, the problem of providing suicient loading to cut stone is enhanced by the fact that the maximum loading that can be applied to the bit at the beginning of the hole, for instance, through hydraulic loading means, is limited by the reactive weight of the derrick itself. Even as the hole gets deeper and weighting can be applied by means of drill collars, the amount of weight that can be practically used is often limited by the strength of the cone-type bit to a value which is insutlicient for eicient cutting of the stone.

The problem of weighting can be alleviated with the use of percussive drilling equipment. While such equipment has been used with rotary, cone-type drilling apparatus, it has been found that for cutting hard rock, as granite, solid-type bits equipped with hardened buttonor wedge-shaped inserts in combination with percussion drill equipment are often more practical and eicient. Nevertheless, the use of an extra large, solid-type bit for making the upper 40 feet of the hole in which the casing is to be set requires more powerful compressor machinery for eflicient operation than is necessary and customarily provided, as indicated above, for drilling the balance of the well. Water well drillers ordinarily do not have such extra powerful compressor equipment and attempt to make do with ordinary equipment which results in delay and inordinate `wear and breakage of the bits.

Accordingly, an object of the present invention is to provide a novel, eicient method of drilling wells, particularly water wells, with their upper portions of substantially greater diameter than the remainders thereof.

Another object is to provide novel hole-enlarging bit equipment of the solid type which is adapted, in coordination with smaller, more conventional bit equipment, to drill all portions of the well while using compressor and rig equipment of a capacity to eiliciently drill the main portion of the Well but which would be inadequate to eliiciently drill the larger upper portion thereof while using a properly proportioned bit of conventional design.

In accordance with the present invention, a rst hole is drilled of substantially the diameter of the main portion of the well and utilizing more-or-less conventional compressor, rig, percussion motor, and bit equipment customarily provided for this purpose. Next, a hole-opener bit of unique design is utilized for enlarging the upper, say, 4() feet of the hole. The novel bit either may be applied to the percussion motor used in making the rst hole, or may be inserted with a different motor of corresponding capacity. Although the compressor equipment used in making the first hole will be adequate to enlarge the upper portion of the first hole, there may be insucient flushing `air passing, upwardly around the enlarging bit to carry larger pieces of debris. Such debris, however, will fall into the bottom of the initial hole of smaller diameter. Next, casing is set in the enlarged hole and cemented, the inner diameter of the casing being substantially the diameter of the smaller portion of the hole extending beneath the enlarged hole, Finally, the original bit of conventional design, applied to the percussion tool, is inserted through the casing and the hole completed to the desired depth. Due to the restrictive elect of the casing in the enlarged part of the hole, adequate ushing fluid velocity will be provided for carrying debris to the top of the hole.

T'he hole-enlarging bit of unique design consists of Ian intermediate cutter portion having an annular forward face provided with cutting inserts of carbide or other hardened material, a forward guide portion of at least approximately the same axial length as the intermediate portion, and a rearward, cylindrical portion of smallest diameter which slidably lits Within fand functions as the anvil portion of the pressure uid operated percussion motor.

In the accompanying drawings which illustrate the invention,

FIGS. 1, 2, and 3 are schematic views illustrating the novel method of drilling a Water well.

FIG. 4 is a perspective side view of the bit.

FIG. 5 is a longitudinal center section through the novel hole-enlarging bit and a portion of the percussion motor.

FIG. 1 illustrates an air compressor 6 mounted on the floor 7 of a drilling derrick 8, floor 7 also mounting a rotary table 9 of conventional design and usual powering means (not shown). The compressor may be the widely available 4commercial unit of 450 Cubic feet per minute at atmospheric pressure. A string of drill pipe 10 extends through the rotary table into a first well bore 11 which is of the diameter desired for the major part of the well, say, 6-6% inches. At the lower end of drill string 10 there is provided a percussion motor 12 which may be of the type illustrated in S. L. Collier and M. E. Schindler Patent No. 3,311,177 and operating `at 100 or 200 pounds per square inch. A rock bit 13 of conventional form for drilling first hole 11 of 6 or 6% inches in diameter, is mounted at the bottom of tool 12. A hose 14 conducts pressured air from compressor 6 to drill string 10, thence downwardly through the string to cause operation of the motor 12 and the application of percussive blows through bit 13 to the bottom of the hole. The initial hole 11 should be drilled somewhat deeper than the portion of the hole which is to be cased.

FIG. 2 shows the upper portion 17 of the hole enlarged to, say, 8 or 10 inches in diameter with the use of a unique hole-opener bit 18 to be described hereafter. Compressor 6 is fully adequate and efficient for this enlarging operation. Larger pieces of debris which may not be carried upwardly through the enlarged hole 17 drop past enlarger bit 18 into the bottom of hole 11, as at 19.

Thereafter, a section of casing 22 is set in the enlarged upper part 17 of the hole, and the annulus filled with cement 23 to seal off the well from ground water and contamination. Finally, hole 11 is completed to the desired depth with the use of the original conventional bit 13, while still using the same compressor equipment 6. Debris 19 will be easily broken up and/or delivered upwardly by bit 13 and the flushing fluid passing therethrough.

The hole-enlarger bit 18, as shown in FIGS. 4 and 5, consists of a forward guide portion 26, an intermediate cutter portion 27, and a rearward anvil portion 28, all of generally cylindrical shape and of varying diameters. Forward portion 26 is of substantially the diameter of the main portion 11 of the wel-l bore and has longitudinally extending flutes 30 and 31 vin its periphery and a central, axial hole 32. Portion 26, prefarably, is of `axial length at least a-pproximating the corresponding dimension of cutter portion 27. Recesses 33 in the forward face of portion 26 connect hole 32 to peripheral flutes 31.

Intermediate cutter portion 27 has a somewhat inclined, forwardly-facing, annular cutter surface 35 in which -are seated inclined cutter buttons or nodules 36 and 37, the latter extending substantially flush with the peripheral surface 38 for maintaining gauge of the hole enlargement. Surface 38 is provided with axial flutes 39 and 40 moreor-less aligned with flutes 30 and 31 in the forward guide portion. An axial hole 41, 41a extends through the intermediate as well as the rear portions of the body and connects with forward flushing hole 32. Inclined flushing holes 43 and 44 extend from axial hole 41 outwardly through the sides of cutter portion 27 opening through key-shaped ports 45.

The rear body portion 28 is of somewhat less diameter than guide portion 26 and has longitudinally spaced annuli designed to slidably fit within percussion motor casing 48 and form the anvil portion of the percussion motor. Threadedly secured to the lower extremity of casing 48 is a split sleeve driver sub 49 having internal flutes matching the external longitudinal flutes 50 on anvil portion 28 for receiving therebewteen guide or spline rollers 51 which enforce joint rotary motion of casing 48 and the enlarger bit, while permitting the bit to fall forward relative to the casing, when the tool is supported off bottom, for stopping the percussive action while producing a continuous flow of operating fluid through the tool and bit, all as explained in the abovementioned patent. At S2 is shown a portion of the hammer piston which is caused to oscillate within casing 42 when the tool is on bottom and operating fluid is being supplied through porting stem 54 to apply percussive blows through the bit to the bottom portion of the hole enlargement. Split collar driver sub 49 can be unscrewed from the bottom of the casing to permit withdrawal of the anvil-bit for sharpening and/or repair and/or replacement thereof. As indicated above, it is contemplated that the anvil portion 28 of the novel hole-enlarger lbit may replace a more-or-les conventional rock bit 13 'at the forward end of the percussion motor 48, 52, etc. Accordingly, the upper portion 41a of the axial exhaust hole through the anvil-bit is constructed to slidably receive the lower extremity S4 of the porting stem extending axially through the casing portion of the percussion motor from the working fluid connection at the upper or rear end of the casing into the anvil-bit exhaust passage, as further explained in the above-mentioned patent.

In drilling a well with the novel hole-opener rock bit, a hole 11, say, 6-6% inches in diameter, will be drilled to a depth of, say, 8O feet-that is, substantially deeper than the length of protective surface casing which is to be provided. A downhole percussion motor 12 equipped with a more-or-less conventional rock bit 13 is used for this purpose and is driven by air compressor 6 and rotary table 9 through which the drill string 10 extends in the usual manner. Next, the novel hole-opener bit illustrated in FIGS. 4 and 5 is substituted for the bit 13 carried by percussion motor 12 or, alternatively, a different percussion motor and bit assembly are mounted on drill string 10 suspended from derrick 8. Enlarged hole portion 17 is then drilled for the distance in which it is desired to set the protective ground casing. For this purpose, the same compressor and rotary table equipment are used. Although the compressor will eiciently operate the holeopener bit under these conditions, since the power requirement will be comparable, there may not be suflicient exhaust air blowing through passage 41, 32 during normal operation of the motor for lifting at least the larger pieces of debris. Such pieces may drop past flutes 30 and 31 in bit guide portion 26 into the bottom of hole 11, as at 19. Next, the protective ground casing 22 is set in the enlarged hole 17 and surrounded with sealing cement 23. Finally, the regular rock bit 13 is reapplied to the percussion motor and the assembly inserted by means of the drill string through casing 22 to the bottom of hole 11 and operated to continue this hole downwardly for the desired depth. Again, the normal compressor 6 will efficiently serve for this purpose, both to continue the drilling of main hole portion 11 and lift the debris upwardly therethrough and through casing 22, the internal diameter of which will be substantially the same as that of hole 11.

The use of the percussion equipment, including rock bit 13 and the hole-opener bit, both of which, preferably, will be provided with carbide inserts, as at 36 and 37, substantially reduces the necessity for weighting of the bit while providing exemplary rock-cutting rate. Moreover, the novel procedure and hole-opener bit make it possible for the well driller to utilize a single compressor for supplying operating fluid to the percussion motoi without forfeit of drilling efficiency, as has been the case heretofore.

The invention may be modified in various respects as will occur to those skilled in the art, and the exclusive use of all modifications as come within the scope of the appended claim is contemplated.

I claim:

1. The method of drilling a well which comprises the steps of utilizing percussion drilling equipment and a first bit to drill a hole of a first diameter in the ground, utilizing the same drilling equipment and a diametrically larger bit to enlarge at least the upper part of said hole, setting and securing protective casing in the enlarged hole part, and utilizing said drilling equipment and said first bit to continue the hole of said first diameter to the desired depth.

2. The method described in claim 1 further including the step of directing at least a portion of the cuttings formed in said enlarging step into the bottom of said rst hole.

3. The method of drilling a Well which comprises the steps of drilling a length of hole by means of a percussion motor, a rst, full hole size cutting bit mounted on said motor, and a compressor of a capacity to operate eiciently with said motor and bit, utilizing a larger bit with said compressor and motor to enlarge a substantial proportion of said hole length, securing casing in said enlarged hole length, and continuing drilling of the hole through said casing with the use of said rst cutting bit, said motor, and said compressor.

4. The method described in claim 3 in which said larger bit is provided with an axial, forward extension of slightly less diameter than said first hole length and substantial axial length for projecting into said rst hole to guide said larger bit.

References Cited UNITED STATES PATENTS DAVID H. BROWN, Primary Examiner U.S. Cl. X.R. 17557, 407 

